Re: [PATCH 10/18] nvme-tcp: fixup send workflow for kTLS

Jakub Kicinski
2023-03-31T05:49:23Z

On Thu, 30 Mar 2023 18:24:04 +0300 Sagi Grimberg wrote:
> > kTLS does not support MSG_EOR flag for sendmsg(), and in general
> > is really picky about invalid MSG_XXX flags.
>
> CC'ing TLS folks.
>
> Can't tls simply ignore MSG_EOR instead of consumers having to be
> careful over it?

I think we can support EOR, I don't see any fundamental problem there.

> > So ensure that the MSG_EOR flags is blanked out for TLS, and that
> > the MSG_SENDPAGE_LAST is only set if we actually do sendpage().
>
> You mean MSG_SENDPAGE_NOTLAST.
>
> It is also a bit annoying that a tls socket dictates different behavior
> than a normal socket.
>
> The current logic is rather simple:
> if more data comming:
> flags = MSG_MORE | MSG_SENDPAGE_NOTLAST
> else:
> flags = MSG_EOR
>
> Would like to keep it that way for tls as well. Can someone
> explain why this is a problem with tls?

Some of the flags are call specific, others may be internal to the
networking stack (e.g. the DECRYPTED flag). Old protocols didn't do
any validation because people coded more haphazardly in the 90s.
This lack of validation is a major source of technical debt :(